Method and apparatus for routing ATM cells in an AD-ATM LAN

Abstract

A system and method for routing ATM cells in a wireless ATM local area network (LAN) that use portable base station (PBS) switching nodes. Routing of cells to and from mobile users within the network is accomplished utilizing a novel routing scheme which preserves cell sequence. Each user transmitting data to another user is associated with a Source Home Station or node and each user receiving data is associated with a Destination Home Station or node. When a connection is established in the network between a first mobile user and a second mobile user, the ATM cells are routed along a fixed path from the first mobile user to the associated Source Home Station and along a fixed path between the Source Home Station to the Destination Home Station and then along a fixed path from the Destination Home Station to the second destination user. In this way cell sequence is maintain by utilizing the Source Home to Destination Home path. Mobile users within the network are also associated with a Local PBS which can be different from the Home Stations as the mobile moves around the network. The Local PBSs associated with the mobile user are slowly updated to be the Home Stations to cure inefficient routing.

What is claimed is: 
     
       1. A communications network for transfer of Asynchronous Transfer Mode (ATM) cells between mobile users, said network comprising: a plurality of relocatable switching nodes, said switching nodes being coupled to one another via a high speed backbone link; and   one or more wireless access links included in each of said switching nodes adapted to couple to said mobile users, wherein a first mobile user transmitting data to a second mobile user in said network is associated with a source home node and said second mobile user receiving data is associated with a destination home node, and wherein said ATM cells in a connection between said first mobile user and said second mobile user are substantially always routed along a path from said first mobile user including said source home node and along a path from said source home node to said destination home node and then along a path including said destination home node to said second mobile user, wherein in-sequence delivery of said ATM cells between said first and second mobile user is enabled to be maintained,   further including a source local node and a destination local node selected from said plurality of switching nodes, said source local node associated with a present position of said first mobile user, and said destination local node associated with a present position of said second mobile user, wherein said ATM cells transmitted from said first mobile user are initially received at said source local node and said ATM cells received at said second mobile user are ultimately transmitted from said destination local node,   wherein said source local node and said destination local node are updatable as a mobile user moves throughout said network.   
     
     
       2. The network of claim 1, wherein said first mobile user, said source local node and said source home node may be different nodes in said network. 
     
     
       3. The network of claim 1, wherein said second mobile user, said destination local node and said destination home node may be different nodes in said network. 
     
     
       4. The network of claim 1, wherein said high speed backbone link of said switching nodes is configurable in an arbitrary ad-hoc topology. 
     
     
       5. The network of claim 1, wherein said source home node and said destination home node associated with said first and second mobile user, respectively, are updatable as said first and second mobile users move throughout said network. 
     
     
       6. The network of claim 1, wherein a VPI (virtual path identifier) for routing said ATM cells within said network corresponds only to a destination node, thereby eliminating a need for translation at intermediate nodes along a route. 
     
     
       7. The network of claim 1, wherein for transmission of a message, said first mobile user requires only an address of said source home node associated with said first mobile user and said second mobile user requires only an address of said destination home node associated with said second mobile user. 
     
     
       8. The network of claim 1, wherein during transmission of a message a source home node only requires an address of a destination home node and not a mobile user destination address. 
     
     
       9. The network of claim 1, wherein said high speed backbone link is adapted for wireless transmission of said ATM cells between said plurality of switching nodes. 
     
     
       10. The network of claim 1, wherein said path between said source home node and said destination home node is fixed during a connection. 
     
     
       11. A communications network for transfer of Asynchronous Transfer Mode (ATM) cells between mobile users, said network comprising: a plurality of relocatable switching nodes, said switching nodes being coupled to one another via a high speed backbone link; and   one or more wireless access links included in each of said switching nodes adapted to couple to said mobile users, wherein a first mobile user transmitting data to a second mobile user in said network is associated with a source home node and said second mobile user receiving data is associated with a destination home node, and wherein said ATM cells in a connection between said first mobile user and said second mobile user are substantially always routed along a path from said first mobile user including said source home node and along a path from said source home node to said destination home node and then along a path including said destination home node to said second mobile user, wherein in-sequence delivery of said ATM cells between said first and second mobile user is enabled to be maintained,   further including a source local node and a destination local node selected from said plurality of switching nodes, said source local node associated with a present position of said first mobile user, and said destination local node associated with a present position of said second mobile user, wherein said ATM cells transmitted from said first mobile user are initially received at said source local node and said ATM cells received at said second mobile user are ultimately transmitted from said destination local node,   wherein said first mobile user may move from a first location to a second location during a connection thereby associating itself with a new source local node, and wherein cell sequence is preserved in said connection by issuance of a "Tail" signal from said source local node associated with said first location.   
     
     
       12. The network of claim 11, wherein said source home node is operable to wait for said Tail signal before serving cells from said second location of said first mobile user. 
     
     
       13. The network of claim 12, wherein said switching nodes include FIFO memory means, and wherein said cells transmitted from said new local node are delayed at said source home node in said FIFO memory until said tail signal is received. 
     
     
       14. A communications network for transfer of Asynchronous Transfer Mode (ATM) cells between mobile users said network comprising: a plurality of relocatable switching nodes, said switching nodes being coupled to one another via a high speed backbone link; and   one or more wireless access links included in each of said switching nodes adapted to couple to said mobile users, wherein a first mobile user transmitting data to a second mobile user in said network is associated with a source home node and said second mobile user receiving data is associated with a destination home node, and wherein said ATM cells in a connection between said first mobile user and said second mobile user are substantially always routed along a path from said first mobile user including said source home node and along a path from said source home node to said destination home node and then along a path including said destination home node to said second mobile user, wherein in-sequence delivery of said ATM cells between said first and second mobile user is enabled to be maintained,   further including a source local node and a destination local node selected from said plurality of switching nodes, said source local node associated with a present position of said first mobile user, and said destination local node associated with a present position of said second mobile user, wherein said ATM cells transmitted from said first mobile user are initially received at said source local node and said ATM cells received at said second mobile user are ultimately transmitted from said destination local node,   wherein said first mobile user may move from a first location to a second location during a connection thereby associating itself with a new source local node, and wherein said source home node associated with said first mobile is operable to record sequence numbers of cells for its own active virtual channels (VCs), wherein said source home node notifies said first mobile user of the last sequence number of a cell received through said new source local node, and wherein said mobile retransmits appropriate cells if the last sequence number differs from said last sequence number received at said source home node.   
     
     
       15. A communications network for transfer of Asynchronous Transfer Mode (ATM) cells between mobile users, said network comprising: a plurality of relocatable switching nodes, said switching nodes being coupled to one another via a high speed backbone link; and   one or more wireless access links included in each of said switching nodes adapted to couple to said mobile users, wherein a first mobile user transmitting data to a second mobile user in said network is associated with a source home node and said second mobile user receiving data is associated with a destination home node, and wherein said ATM cells in a connection between said first mobile user and said second mobile user are substantially always routed along a path from said first mobile user including said source home node and along a path from said source home node to said destination home node and then along a path including said destination home node to said second mobile user, wherein in-sequence delivery of said ATM cells between said first and second mobile user is enabled to be maintained,   further including a source local node and a destination local node selected from said plurality of switching nodes, said source local node associated with a present position of said first mobile user, and said destination local node associated with a present position of said second mobile user, wherein said ATM cells transmitted from said first mobile user are initially received at said source local node and said ATM cells received at said second mobile user are ultimately transmitted from said destination local node,   wherein said second mobile user is operable to update said local destination node by sending a signaling request including a sequence number of a last received cell through the new local node to said destination home node, and said destination home node is operable to retransmit appropriate ATM cells to said new local node if the last sequence number transmitted from said destination home node does not match said sequence number of said last received cell at said second mobile user.   
     
     
       16. A method for routing ATM cells in a network of mobile users which includes a plurality of high speed switching nodes adapted to be coupled to one another, said method comprising the steps of: establishing a source home node for a source mobile user and a destination home node for a destination mobile user for use in a connection between said source user and said destination user; and   routing said ATM cells along a path from said source mobile user including said source home node, and along a path from said source home node to said destination home node, and then along a path including said destination home node to said destination user,   further including the step of establishing a local node associated with a present position of a mobile user, wherein data transferred to and from said mobile user travels through said local node, wherein said local node and said source home node for a mobile user may be different nodes in said network and said local node and said destination home node for a mobile user may be different nodes in said network,   further including the step of updating said local node to be said source home node and updating said local node for said mobile user to be said destination home node.   
     
     
       17. The method of claim 16, wherein said plurality of high speed switching nodes are adapted for wireless coupling between one another. 
     
     
       18. The method of claim 16, wherein said plurality switching nodes couple to one another to form a high speed backbone link configurable in arbitrary ad-hoc topology. 
     
     
       19. A method for routing ATM cells in a network of mobile users which includes a plurality of high speed switching nodes adapted to be coupled to one another, said method comprising the steps of: establishing a source home node for a source mobile user and a destination home node for a destination mobile user for use in a connection between said source user and said destination user; and   routing said ATM cells along a path from said source mobile user including said source home node, and along a path from said source home node to said destination home node, and then along a path including said destination home node to said destination user,   further including the step of establishing a local node associated with a present position of a mobile user, wherein data transferred to and from said mobile user travels through said local node,   wherein a mobile user may move from a first location to a second location during a connection thereby associating itself with a new local node, and wherein a procedure for updating a source local node includes the step of issuing a "Tail" signal from a local node associated with said first location through the old local node, and waiting at said source home node for said Tail signal before serving cells from said second location of said mobile.   
     
     
       20. The method of claim 19, further including the steps of: generating from said mobile user a handoff request to said new local node;   forwarding said handoff request to said source home node through said old local node;   setting up a connection between said new local node and said source home node; and   notifying said mobile user from said new local node of a new VPI and VCI.   
     
     
       21. A method for routing ATM cells in a network of mobile users which includes a plurality of high speed switching nodes adapted to be coupled to one another, said method comprising the steps of: establishing a source home node for a source mobile user and a destination home node for a destination mobile user for use in a connection between said source user and said destination user; and   routing said ATM cells along a path from said source mobile user including said source home node, and along a path from said source home node to said destination home node, and then along a path including said destination home node to said destination user,   further including the step of establishing a local node associated with a present position of a mobile user, wherein data transferred to and from said mobile user travels through said local node,   wherein a mobile user may move from a first location to a second location during a connection thereby associating itself with a new local node, and wherein a procedure for updating a source local node includes the steps of: generating from said mobile user a handoff request to said new local node;   forwarding said handoff request to said source home node through said old local node;   setting up a connection between said new local node and said source home node;   notifying said mobile user from said new local node of a new VPI and VCI and a sequence number of a last received one of said ATM cells; and   retransmitting from said destination home node appropriate ones of said ATM cells if said sequence number is not equal to the sequence number of its last transmitted cell.     
     
     
       22. A method for routing ATM cells in a network of mobile users which includes a plurality of high speed switching nodes adapted to be coupled to one another, said method comprising the steps of: establishing a source home node for a source mobile user and a destination home node for a destination mobile user for use in a connection between said source user and said destination user; and   routing said ATM cells along a path from said source mobile user including said source home node, and along a path from said source home node to said destination home node, and then along a path including said destination home node to said destination user,   further including the step of establishing a local node associated with a present position of a mobile user, wherein data transferred to and from said mobile user travels through said local node,   wherein a mobile user may move from a first location to a second location during a connection thereby associating itself with a new local node, wherein the old local node was the same node as said source home node, a procedure for updating a source local node and preserving a sequence of said ATM cells including the steps of: generating from said mobile user a handoff request to said new local node;   forwarding said handoff request to said source home node;   setting up a connection between said new local node and said source home node;   notifying said mobile user from said new local node of a new VPI and VCI.     
     
     
       23. A method for routing ATM cells in a network of mobile users which includes a plurality of high speed switching nodes adapted to be coupled to one another, said method comprising the steps of: establishing a source home node for a source mobile user and a destination home node for a destination mobile user for use in a connection between said source user and said destination user; and   routing said ATM cells along a path from said source mobile user including said source home node, and along a path from said source home node to said destination home node, and then along a path including said destination home node to said destination user,   further including the step of establishing a local node associated with a present position of a mobile user, wherein data transferred to and from said mobile user travels through said local node,   wherein a mobile user may move from a first location to a second location during a connection thereby associating itself with a new local node, and wherein a procedure for updating a destination local node includes the steps of: generating from said mobile user a handoff request to said new local node with a sequence number included of a last one of said ATM cells received;   forwarding said handoff request to said destination home node through the old local node;   setting up a connection between said new local node and said source home node;   notifying said mobile user from said new local node of a new VPI and VCI; and   retransmitting form said mobile user appropriate ones of said ATM cells if said sequence number is not equal to the sequence number of its last transmitted cell.